JPH0895272A - Photoreceptor drum - Google Patents

Abstract

PURPOSE: To provide a photoreceptor drum capable of preventing the generation of oscillating noise at the time of electrification without causing the dielectric breakdown of the photosensitive layer and having high resolution as the photoreceptor drum used in a laser beam printer adopting a contact electrification system. CONSTITUTION: A single layer type photosensitive layer contg. 1 part gallium phthalocyanine pigment dispersed in 2-10 parts binder is formed on a stainless steel substrate having surface toughness Rmax of <=2.0μm obtd. by grinding the surface of a stainless steel pipe to produce the objective photosensitive drum 1. The stainless steel pipe preferably has diameter of <=30mm and thickness of >=0.4mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive drum using a stainless steel substrate, and in particular, it prevents discharge damage of the photosensitive drum due to contact charging and generation of vibration noise during charging.
Further, the present invention relates to a photosensitive drum that brings about an improvement in resolution during digital exposure.

[0002]

2. Description of the Related Art Conventionally, a non-contact type corona discharge device has been generally used as a charging device in an electrophotographic apparatus using a photosensitive drum. However, in recent years, since the power source can be reduced in voltage and ozone is generated in an extremely small amount, there are advantages such as a roller type, a blade type, and a brush type charging member to which a voltage is applied. A contact charger using is being used. When charging by a contact charger, there are a method of applying a direct current and a method of applying an oscillating voltage in which an alternating current is superimposed on a direct current. By the way, when the above-described oscillating voltage is applied to the charging roller to charge the photosensitive drum, cycle unevenness in the circumferential direction of the photosensitive drum tends to occur as the peripheral speed of the photosensitive drum increases, and this is prevented. Therefore, the frequency of the vibration voltage applied to the charging roller must be increased. However, the frequency is about 200H
If z is exceeded, there is a problem in that a so-called charging noise is increased due to vibration of the photosensitive drum and the charging roller. There is also a problem that sliding noise is generated due to friction with the cleaning blade.

The generation of such charging noise and sliding noise (hereinafter referred to as vibration noise) causes the thickness of the base of the photosensitive drum to be 2
This is especially likely to occur in the case of thin-walled aluminum pipes of mm or less. In order to prevent the generation of such a vibration sound, for example, Japanese Patent Laid-Open Nos. 3-105348 and 5-
In Japanese Patent No. 34936, etc., it is proposed to put a filler inside the photosensitive drum to reduce vibration noise of the photosensitive drum. On the other hand, when a pipe other than the aluminum pipe, for example, a pipe made of stainless steel is used, no vibrating noise is generated without inserting the filler. However, when contact charging is applied to a photosensitive drum using a stainless steel pipe as a substrate, there is a problem that the photosensitive layer is easily broken by abnormal discharge during charging. This phenomenon is considered to be due to the following reasons. That is, in the case of the contact charger, the current capacity is larger than that of the corona charger, so if there is a weak withstand voltage in the photosensitive layer, the current concentrates there and the current flows until discharge breakdown occurs. Occurs. When the photosensitive layer is destroyed, not only the electric charge is not applied to that portion and an image defect is caused, but also the charging member may be destroyed by an abnormal current, and as a result, uniform charging can be almost expected. Disappear.

On the other hand, in a laser printer that digitally exposes a photosensitive drum with a laser beam, further miniaturization and high resolution are required. The miniaturization can be achieved by using a photosensitive drum having a diameter of 30 mm or less. For high resolution, those having high γ characteristics described in Japanese Patent Publication No. 5-19140 are suitable. That is, since the laser spot has a skirt spread of the light (Gaussian distribution), if the faithful reproduction of the laser spot causes blur of the dot boundary and the resolution cannot be improved, if the photosensitive layer has a high γ characteristic, the skirt spread is weak. Since it is not sensitive to light, the boundaries of dots can be made clear. In order to obtain such high γ characteristics, it is necessary to induce an induction effect or an avalanche phenomenon in a single-layer photosensitive layer in which an OPC pigment is dispersed in a binder resin.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to obtain an optimum photosensitive drum for a laser printer by optimally combining all these conditions.

[0006]

The photosensitive drum of the present invention comprises:
After forming an undercoat layer on a stainless steel substrate having a surface roughness Rmax of 2.0 μm or less, 1 part (parts by weight, the same applies hereinafter) of gallium phthalocyanine pigment is added in an amount of 2 to 2.
It is characterized in that a photosensitive layer formed by being dispersed in 10 parts of a binder is formed.

The electrostatic charge damage that occurs when the photosensitive drum using a stainless steel pipe is subjected to contact charging is caused by abnormal projections on the surface of the substrate. That is, since the stainless steel pipe has a higher hardness than the aluminum pipe, the protrusions existing on the surface are less likely to be smooth, and moreover, the protrusions are left in an acute angle state, so that abnormal discharge is likely to occur. Therefore, the first object could be achieved by smoothing the surface of the stainless steel pipe. Further, in the present invention, the diameter of the stainless steel pipe is 30
mm or less is used, in which case the wall thickness is 0.4
It is preferably at least mm. If the wall thickness is less than 0.4 mm, the vibration noise prevention effect becomes insufficient. Further, if the wall thickness is too thick, the weight becomes large and it becomes difficult to use, so that the thickness is preferably 2 mm or less.

A description will be given below with reference to the drawings. FIG. 1 is a sectional view of an essential part of a laser printer in which a photosensitive drum is used. In the figure, the charging roll 2 is disposed so as to contact the surface of the photosensitive drum 1. As the charging roll, one having a structure in which a layer made of a conductive elastic material is formed on the core material 3 is used. A direct current voltage or a direct current voltage on which an alternating current component is superimposed is applied to the core material 3 from a power source (not shown).

In the present invention, the conductive support is produced by grinding the surface of a stainless steel pipe so that the surface roughness Rmax is 2.0 μm or less. However, Ra is preferably 0.1 μm or more in order to prevent the occurrence of an interference fringe pattern that occurs when the laser beam is irradiated. The surface of the stainless steel pipe can be ground with a rotary grindstone, sandpaper, a grinding film, or the like.

FIG. 4 is a schematic configuration diagram of a centerless grinding apparatus for grinding the surface of a stainless steel pipe.
The centerless grinding apparatus is composed of three sets of grindstones consisting of a pair of opposing rotary grindstones, namely grindstones 5 and 5, grindstones 6 and 6, grindstones 7 and 7, and grindstones 5 and 6,
It consists of fine abrasive grains in the order of 7. The pair of rotating grindstones facing each other are installed so that the rotating speeds thereof are different from each other, whereby the stainless steel pipe 4 placed thereon is rotated. In addition, the intervals of the respective rotating grindstones facing each other can be adjusted, whereby the stainless steel pipes are moved from the grindstones 5, 5 to the grindstone 6,
6, then to the grindstones 7, 7. In this grinding machine, stainless steel pipe 4
Is placed on two rotating grindstones 5 and 5, and is ground while rotating, and is sequentially ground by the grindstones 6 and 6 and grindstones 7 and 7.

FIG. 5 is a schematic diagram of another grinding apparatus for grinding the surface of a stainless steel pipe. In this case, a grinding film 9 coated with polishing powder is used, sent out from a roll 10, and pressed against the surface of the rotating stainless steel pipe 4 by a pressing roll 8 with an appropriate pressure. The grinding film is a take-up roll 11
Is taken up by.

In the present invention, the surface roughness Rmax of the conductive substrate is 2.0 μm or less, and since there are no high protrusions, when contact charging is performed, the photosensitive layer causes abnormal discharge. It is possible to prevent discharge breakdown of the photosensitive layer and to uniformly charge the photosensitive layer. This will be described with reference to FIGS. 2 and 3. FIG. 2 shows the result of measuring the roughness of the surface of the stainless steel pipe, and high protrusions exceeding 2 μm are recognized here and there. The surface roughness Rmax is 3.5 μm.
If such a stainless steel pipe is used as it is, the problems as described in the above-mentioned conventional technique occur. On the other hand, in the present invention, the stainless steel pipe is ground to obtain the surface roughness Rma.
x is 2.0 μm or less. FIG. 3 shows an example thereof, and shows the result of measuring the surface roughness of a ground stainless steel pipe. As is clear from FIG. 3, no protrusion exceeding 2 μm was observed,
The surface roughness Rmax is 2.0 μm or less. Note that Rmax is preferably 0.1 μm or more in order to prevent the generation of an interference fringe pattern that occurs when the laser beam is irradiated.

As described above, in the present invention, the conductive support made of stainless steel is used, and its surface roughness Rmax is
Is 2.0 μm or less, and therefore, when the photosensitive layer formed thereon is contact-charged, abnormal discharge of the photosensitive layer is less likely to occur, discharge breakdown of the photosensitive layer can be prevented, and uniform Can be charged. Further, in the present invention, since a conductive substrate formed of stainless steel having a higher specific gravity than aluminum is used, vibration noise generated by contact or sliding by a contact charger or cleaning blade is used. Can be prevented.

On the other hand, the photosensitive layer is formed with a single-layer type photosensitive layer in which a pigment is dispersed in a binder. When galimphthalocyanine whose central metal is gallium is used as the pigment and the single layer type photosensitive layer is formed by dispersing 1 part of the pigment in a ratio of 2 to 10 parts of the binder, the induction effect easily occurs. Therefore, high γ characteristics can be obtained. In particular, as a binder, JP-B-5-19140 and JP-A-6-9541 are used.
As described in Japanese Unexamined Patent Publication No. No. 0-0,036, high γ characteristics can be easily obtained without requiring a resin having a resistance of 10 ¹³ Ωcm or more. It is considered that this is because the volume resistivity of gallium phthalocyanine is sufficiently high. As gallium phthalocyanine, crystalline chlorogallium phthalocyanine described in JP-A-5-98181 or crystalline hydroxygallium phthalocyanine described in JP-A-5-279591 is preferable. The thickness of the photosensitive layer is preferably about 5 to 30 μm.

An undercoat layer may be provided below the photosensitive layer. This is to improve the adhesion between the photosensitive layer and the substrate, improve the coatability of the photosensitive layer, protect the substrate, cover defects on the substrate, protect the photosensitive layer from electrical breakdown, and improve the carrier injection property of the photosensitive layer. It is provided for improvement. For this material,
Polyurethane, polyamide, polyvinyl alcohol, epoxy resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, casein, methyl cellulose,
Organic resins such as nitrocellulose and phenol resins and / or known materials such as zirconium chelate compounds, titanyl chelate compounds, titanyl alkoxide compounds, organic titanyl compounds and silane coupling agents can be used. The thickness of the undercoat layer is 0.01 to
It is 10 μm, preferably 0.05 to 2 μm. A protective layer may be provided on the photosensitive layer to improve durability.

In FIG. 1, the photosensitive drum 1 is exposed to a laser beam 21. Reference numeral 22 is a mirror, which is exposed to form a latent image, is developed by a developing device 23, and a toner image is transferred onto a print paper 25 by a transfer roll 24.
26 is a cleaner. The spot of the laser light has a skirt of light due to a Gaussian distribution, but if it irradiates the photosensitive layer having a high γ characteristic, the part of the tail is cut, so that a sharp image quality can be obtained.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 and Comparative Example 1 30 mmφ × 253 mmL × 0.4 mmt SUS30
4 pipes were prepared, and the surfaces of the pipes were ground by the centerless grinding device shown in FIG. What was taken out at the stage of rough cutting had a surface roughness Rmax = 3.
It was 5 μm and Ra = 0.40 μm (Comparative Example 1). What was ground with a finer grindstone had the surface roughness shown in FIG. 3, where Rmax = 1.8 μm and Ra = 0.22 μ.
m (Example 1). These pipes are used as a conductive base, and type 8 nylon resin (Toresin F3
0, manufactured by Teikoku Kagaku Co., Ltd.) was applied to form a subbing layer having a film thickness of 1 μm. JP-A-5
1 part of the chlorogallium phthalocyanine crystal described in JP-A-98181 is used as a polyvinyl butyral resin (BL-
1, 1, Sekisui Chemical Co., Ltd.), 10 parts of cyclohexanone, and 10 parts of tetrahydrofuran, and dispersed in a sand mill. This is a dispersion liquid having a PB ratio of 1: 2. To this, only the resin solution was weighed and added to obtain a PB ratio of 1: 3 and 1: 2.
Dispersions of 4, 1: 6, 1:10, 1:15 were also made. These dispersions were applied on the substrate of the example so as to have a film thickness of 15 μm, to prepare a photosensitive drum.

These photosensitive drums were charged with a charging roll. The charging roll used was as follows. That is, an elastic layer made of polyether-based polyurethane rubber to which 0.5% lithium perchlorate was added so as to have conductivity was formed on the outer circumference of a 5 mmφ stainless steel shaft so as to have a thickness of 15 mmφ, and 0% was formed on the surface. A coating solution comprising a polyester-based polyurethane emulsion resin aqueous solution added with 0.001% methylphenyl silicone leveling agent was applied by a dip coating method and dried at 120 ° C. for 20 minutes to form a coating layer having a thickness of 20 μm. Using. Furthermore, it was mounted on a printer equipped with a semiconductor laser image writing device, a one-component toner developing device, a transfer device, and a cleaning device equipped with a urethane rubber blade,
An evaluation was made. First, a voltage obtained by superposing AC 1000 V on DC +400 V was applied to the charging roll, the exposure intensity was changed, and the photosensitive drum was irradiated with the light, and the light attenuation characteristic of the photosensitive drum was examined. The results are shown in FIG. The horizontal axis of the graph is the exposure amount, and the vertical axis is the surface potential of the photosensitive drum. In the figure,
31 is PB ratio 1: 2, 32 is 1: 3, 33
Is 1: 4, 34 is 1: 6, 35 is 1:10, 36 is 1:
The characteristics of 15 photosensitive layers are shown respectively. It was found that as the binder ratio increases, the light intensity at which the surface potential drops sharply shifts to the right (that is, the sensitivity decreases). PB
When the ratio was 1:15, the sharp potential drop disappeared and the high γ characteristic was lost. The sensitivity can be adjusted within the PB ratio range of 1: 2 to 1:10. Then, reverse image exposure was performed and the print image was evaluated. As a result, in the case of the photoconductor drum of Example 1, an image of good quality without interference fringe patterns and image defects such as black and white dots was obtained. On the other hand, in the case of Comparative Example 1, an abnormal current flows at the time of contact charging, and black spots frequently occur when the image is viewed. This is because the photosensitive layer was destroyed by the abnormal discharge and no electric potential was applied to that portion, and it appeared as a black dot because it was an inverted image. When the surface of the photosensitive drum corresponding to the black spots was examined, it was found that the metal was exposed and that the abnormal protrusion on the surface of the substrate was the cause.

Comparative Example 2 A photosensitive drum was produced in the same manner as in Example 1 except that a stainless steel pipe having a wall thickness of 0.2 mm was used. When this was charged in the same manner as in Example 1, an image with good image quality without image defects such as black and white dots was obtained. However, a small charging noise called peen was generated during contact charging. Comparative Example 3 As a conductive substrate, 30 mmφ × 253 mmL × 0.8
An mmt aluminum pipe was used. The surface roughness was Rmax = 1.8 μm and Ra = 0.15 μm. A photosensitive drum was produced in the same manner as in Example 1 except that this was used. When this was charged in the same manner as in Example 1, a charging sound called pea was generated during contact charging.

[0020]

Since the electrophotographic photosensitive drum of the present invention uses a conductive substrate formed of stainless steel having a specific gravity heavier than aluminum, contact charging is performed by applying a DC voltage with an AC component superimposed. Even if it goes, no vibration noise is generated from the photosensitive drum. In addition, an abnormal projection is scraped off by grinding on the surface of the conductive substrate, and Rmax
Is 2.0 μm or less, it is possible to prevent image defects such as black spots and white spots without causing electrostatic breakdown of the photosensitive layer. Further, since the photosensitive layer has a high γ characteristic, when imagewise exposure is carried out with a laser beam, a high resolution image quality with clear dot boundaries can be obtained. Therefore, the photosensitive drum of the present invention can be used in a laser printer to obtain a high-quality printed image without image defects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a laser printer in which a photosensitive drum is used.

2 shows the measurement results of the surface roughness of the substrate in Comparative Example 1. FIG.

FIG. 3 shows the measurement results of the surface roughness of the substrate in Example 1.

FIG. 4 is a schematic configuration diagram of an example of a centerless grinding device.

FIG. 5 is a schematic configuration diagram of another surface grinding apparatus.

FIG. 6 shows a light attenuation characteristic graph of the photosensitive drum according to the example.

[Explanation of symbols]

1 ... Photosensitive drum, 2 ... Charging roll, 3 ... Core material, 4 ... Stainless steel pipe, 5, 6 and 7 ... Rotating grindstone, 8 ... Pressing roll, 9 ... Grinding film, 10 ... Roll, 11
... Winding roll, 31 ... Light attenuation characteristic of photosensitive layer having PB ratio of 1: 2, 32 to 36 ... Light attenuation characteristic of photosensitive layer having other PB ratio.

Claims (4)

[Claims] 1. A single-layer type photosensitive layer having 1 part of a gallium phthalocyanine pigment dispersed in 2 to 10 parts of a binder is formed on a stainless steel substrate having a surface roughness Rmax of 2.0 μm or less. A photosensitive drum characterized in that 2. The photosensitive drum according to claim 1, wherein the substrate is formed by grinding the surface of a stainless steel pipe to have a surface roughness Rmax of 2.0 μm or less. 3. The substrate has a diameter of 30 mm or less and a wall thickness of 0.4.
The photosensitive drum according to claim 1, which is a stainless steel pipe having a diameter of at least mm. 4. The photosensitive drum according to claim 1, wherein the photosensitive drum is used in a printer which is charged by a contact charger and is digitally exposed by laser light.